Where is Limonite Concretion found?
Hydrous iron oxide
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Open the appLimonite Concretion occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Limonite Concretion
Worldwide
Limonite concretions are extremely common and can be found in virtually any region with iron-bearing rocks and suitable weathering conditions. Notable occurrences include sedimentary basins, bog iron deposits, and lateritic soils.
United States
Abundant in many states, particularly in sedimentary rock formations of the Appalachian Basin, Gulf Coastal Plain, and Midwest. Often found in stream beds, road cuts, and agricultural fields.
Europe
Common in iron-rich sedimentary sequences and bog iron deposits across various countries, including the UK, Germany, and France.
Collecting tips
- Look in Sedimentary Rocks. Search in sandstones, shales, and limestones, especially those that show signs of iron staining or weathering. Road cuts, stream banks, and quarries are good places to look.
- Check for Rusty Stains. Limonite often forms from the oxidation of other iron minerals (like pyrite). Look for areas with rusty-brown staining on rocks or in soil, as concretions may be present.
- Examine Stream Beds and Beaches. Water action can concentrate concretions. Look for rounded, heavy, dark brown to black nodules in gravels and sands.
- Test the Streak. A key diagnostic is the yellowish-brown streak. Carry an unglazed porcelain streak plate to confirm.
- Consider Weight. Limonite concretions are relatively dense due to their iron content, so they will feel heavier than typical rock fragments of the same size.
Quick Check
- Color:
- Yellow-brown to dark brown/black
- Luster:
- Earthy to sub-metallic
- Streak:
- Yellowish-brown
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